8Feldstein, Martin. The optimal level of social security benefits[J]. Quarterly Journal of Economics, 1985,100(2) :303-319.
9Casey B Mulligan, Xavier, Sala-i-Martin. Social security in theory and practice (1) :Facts and political theories[R]. NBER Working Paper No. 7118,1999.
10Vincenzo Galasso,Paola Profeta. The political economy of social security: a survey[J]. European Journal of Political Economy, 2002,18 : 1-29.
